By resolving objections in the prior art, provided are a novel copolymer suitable as a coating polymers which is excellent in adhesion to a substrate and can be used suitably as the polymer for the coating film having durability against pattern collapse in the finer pattern formation for progressed lithography technology and a method for producing the copolymer, as well as a novel thiol compound useful as a chain transfer agent in the production of the copolymer. The novel thiol compound of the present invention has the structure represented by the formula (1); ##STR00001## wherein R.sup.1 is a bivalent substituent selected from linear, branched or cyclic saturated hydrocarbon having 1 to 15 carbon atoms.